Comparison of the total number of the radar astronomy transmissions
with respect to that used for sending messages to extra-terrestrial
civilizations reveals that the probability of detection of the radio signals to
extraterrestrials (ETs) is one million times smaller than that of the radar
signals used to study planets and asteroids in the Solar System.

There are three large-dish instruments in the world that
are currently employed for doing radar investigations of planets, asteroids and
comets [1]: ART (Arecibo Radar Telescope), GSSR (Goldstone Solar System Radar),
and EPR (Evpatoria Planetary Radar). Radiating power and directional diagram of
these instruments is so outstanding that it also allows us to emit radio
messages to outer space, which are practically detectable everywhere in the
Milky Way. This dedicated program is called METI (Messaging to
Extra-Terrestrial Intelligence) [2], as contrasted to SETI (Search for
Extra-Terrestrial Intelligence), [3].
Recently, some scientists and SF writers have expressed their concern [4] that
sending messages to the stars in our galaxy, which may have a habitable life,
jeopardizes existence of our own civilization because our signals helps ETs to
pin down location of the Solar System in the Milky Way. If the Aliens reached
the level of a super-civilization, it might send a space fleet to the Earth to
either destroy it or to convert us to slaves.

The goal of this letter is to estimate the probability
of detection of theterrestrial radio signals by a presumable hostile
super-civilization existing somewhere in our galaxy. Our calculation starts
from the notice that over all the radar astronomy history about 1,400 sets of
radio transmissions were produced. Their distribution all over the sky is shown
in Figure 1 in the plane of
ecliptic coordinates.

The total area of the sky illuminated by these
transmissions, is about 0.022 steradians (sr), or about 2·10-3 part
of the whole sky. The total number of METI transmissions is 16 sets only [5],
and the total area of sky, illuminated by the METI transmissions, is about 10-5
sr, or 2000 times less than that covered by radar astronomy transmissions, Figure
2.

Total duration of time of radar transmissions exceeds the
overall time interval of the METI transmissions by a factor of 500. Therefore,
we can conclude that the probability to detect the radar astronomy
transmissions by a hostile super-civilization is 2000 × 500 = 1,000,000
times higher than that of the METI transmissions.

So, if someone is concerned about our detection by an
aggressive super-civilization (so-called METI-phobia, [6]), first of all
one has to prohibit not the METI, but the radar astronomy. However, one can not
prohibit it because the radar astronomy is an important and indispensable
component of the asteroid hazard and defense system [7]. For this reason, we conclude
that all on-going conversations about the ETs danger of METI for our
civilization are meaningless, and the radar astronomy instruments should remain
open for doing further exploration of the interstellar space with METI
transmissions.